Doors for vans

ABSTRACT

A roll-up door for a container body of a van or the like is provided with a winch which is located in a compartment formed in the header of the door. The winch is connected by flexible winding straps to the upper door panel and the lower door panel so that it is operable to drive the door between the open and closed position. The door panels are hingedly connected by hinges in which the hinge pin is located at the inner face of the door. Flexible sealing members are connected to each jamb and bear against a marginal edge portion of the outer face of the door when the door is in the closed position. A control system for controlling the direction of rotation of the reversible D.C. motor is provided which includes a master control circuit and a slave control circuit which is selectively operable. The control circuit permits the movement of the door to be arrested at any time and to be reversed at any time by operating the master control and allowing similar control by means of the slave control when it is activated.

BACKGROUND OF THE INVENTION

This invention relates to a drive mechanism for raising and lowering aroll-up door.

Roll-up doors are used as garage doors and as doors for vans and trucks.

A drive mechanism for raising and lowering a roll-up door is disclosedin U.S. Pat. No. 4,191,237 Voege dated Mar. 4, 1980. In this mechanismsmall diameter cables are wound onto winding drums. In accordance withconventional practice, the winding drums will be proportioned to permitthe cable to be fully wound onto the drum without overlapping such thatthe wind in speed and pay out speed of the two cable systems areidentical. While this mechanism does incorporate a clutch, the clutch isprovided to permit the drive to slip in the event that the door strikesan obstruction when it is being driven to the open position or to theclosed position.

SUMMARY OF INVENTION

It is an object of the present invention to provide a drive mechanismfor raising and lowering a roll-up door which provides maximum torqueduring the initial raising stage and a progressively increasing liftingspeed.

According to one aspect of the present invention there is provided adrive mechanism for raising and lowering a roll-up door which includes aprimary drive shaft, first and second winding spools, first and secondwinding straps and a slipping clutch. The first and second windingspools are mounted on the primary drive shaft and each have a windingdrum. The first and second winding strap each have a first and secondend mounted on the winding drums of the first and second spoolsrespectively. The second end of the first strap is connected to one endof the roll-up door and the second end of the second strap is connectedto the other end of the roll-up door. The winding drums and straps areproportioned to cause each successive turn of each strap to be woundupon one another as the strap is wound in such that the effectivediameter of the winding surface of each winding drum will vary as itsassociated strap is wound in or paid out. The slipping clutchcommunicates between the primary drive shaft and one of the windingspools to permit said one of the winding spools to slip with respect tothe primary drive shaft to accommodate the difference between theeffective diameter of the winding surface or the winding drums such thatthe first and second winding drums may both be driven by the primarydrive shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial view illustrating a roll-up door in a partiallyopen position,

FIG. 2 and 2a is a partially sectioned enlarged detail view of a portionof the door of FIG. 1.

FIG. 3 is a pictorial view of the drive mechanism of FIG. 1,

FIG. 4 is a sectional view taken along the line 4--4 of FIG. 1,

FIG. 5 is a sectional view taken along the line 5--5 of FIG. 1,

FIG. 6 is a sectional view of the clutch mechanism associated with thedoor closing mechanism.

FIG. 7 is a pictorial view of the latching mechanism which holds thedoor closed.

FIG. 8 is a sectional side view of a portion of the latching mechanismin a closed position.

FIG. 9 is a diagram illustrating a control circuit for use incontrolling the opening and closing of the door of FIG. 1,

FIG. 10 is a pictorial view of a latch socket constructed in accordancewith an embodiment of the present invention,

FIG. 11 is a plan view of a latch plug,

FIG. 12 is a sectional view taken along the line 12--12 of FIG. 11.

With reference to FIG. 1 of the drawings, the reference numeral 10refers generally to a door assembly constructed in accordance with anembodiment of the present invention. The door assembly 10 includes adoor 12, a pair of guide tracks 14 and a winch mechanism 16. The door 12consists of a plurality of door panels 18 which are hingedly connectedin an edge-to-edge relationship by means of hinges 20. The door panels18 include an upper door panel 18a and a lower door panel 18b.

The guide tracks 14 each have an upright portion 14a, a curved portion14b and a generally horizontally extending portion 14c.

A portion of a container body in which the roll-up door of the presentinvention may be located is generally identified by the referencenumeral 22 and is shown in broken lines in FIG. 1 for the purposes offacilitating illustrations of the door mechanism. The container body 22includes a top wall 24, a pair of side walls 26 and a floor 28. Aloading doorway 30 is formed at one end of the container body. Thedoorway 30 is surrounded by a sill 32, a pair of jam members 34 and aheader 36.

A header cavity 38 is formed inwardly of the header 36. The headercavity 38 is bounded by the outer wall 36a of the header 36, theadjacent portion of the top wall 24 and the path of travel of a doorpanel 18 as it is driven around the curved portion 14b of the guidetrack. It will be apparent that when the door is in the opened positionin which the lower panel 18b will assume the position in which the panel18c is illustrated in FIG. 1, the winch mechanism 16 will not be exposedto or visible from within the storage chamber of the container body.

Winch Mechanism

The winch mechanism 16 will now be described with reference to FIGS. 1,3, 4 and 6 of the drawings. As shown in FIG. 3 of the drawings, thewinch mechanism 16 includes a reversible D.C. motor 40 which isdrivingly connected to a primary drive shaft 44 through a reductiongearbox 42. A first pair of winding spools 46 are secured to oppositeends of the shaft 44 and are secured thereto so as to be rotatablydriven in either direction in response to rotation of the shaft 44. Asecond spool 48 is connected to the shaft 44 through a clutch mechanismgenerally identified by the reference numeral 50. The clutch mechanism50 is designed to permit the spool 48 to slip as required in use toaccommodate the differences between the rate of winding in on the spools46 as compared to the rate of paying out on the spool 48.

As shown in FIG. 6 of the drawings, the clutch mechanism 50 includes asleeve 52 which is mounted on one-way clutch collars 54. The sleeve 52is formed with an annular flange 56 at one end thereof. A disc 58 isslidably mounted on the sleeve 52 for movement toward and away from theflange 56. A compression spring 59 bears against the disc 58 and againsta collar 60 which is fixed with respect to the sleeve 52. The spool 48is formed with a bore 62 which will receive the sleeve 52 in a closefitting sliding relationship so that the sleeve 48 can rotate on thesleeve 52. The spool 48 has a winding drum portion 64 and a pair ofoppositely disposed side flanges 66. Annular clutch plates 68 which aremade from a bearing material such as bronze or the like are locatedbetween the side flanges 66 and the annular flange 56 and the disc 58and serve to permit the spool 48 to slip with respect to the sleeve 52and thus the shaft 44 so as to accommodate variations in the rate ofpayout and wind-in required to be consistent with that of the fixedfirst spools 46.

The first spools 46 are connected by means of a first flexible strapmember 70 to a pin 72 which is mounted on an angle bracket 74 which islocated adjacent the lower edge of the lower door panel 18b (FIG. 4).The other end of the strap 70 is anchored with respect to the drumportion of the spool 46. The strap 70 is proportioned to be of a widthwhich is only slightly less than the width of the drum portion of thespool 46 so that successive turns of the strap 70 will wound upon oneanother on the winding drum of the first spool 46 when the first spool46 is wound in the direction to cause winding in of the strap 70.

The second flexible strap member 76 has one end secured to the upperedge of the upper door panel 18a by means of a latch slate assembly 270(FIG. 2), the other end of the strap member 76 is secured to the windingdrum portion 64 of the spool 48. The winding drum portion 64 isproportioned to ensure that successive turns of the strap member 76 willbe wound upon one another when the strap 76 is wound onto the spool 48.

It will be apparent that the rate at which the straps 70 and 76 arewound in or paid out from their respective spools will vary as theeffective diameter of the winding surface changes because of thethicknesses of the strap located on the spool at any particular time. Aspreviously indicated, the first spools 46 are secured with respect tothe shaft 44 and consequently these variations in the relative wind inand payout speed are accommodated by the fact that the second spool 48can slip with respect to the primary drive shaft 44. The one-way clutchcollars 54 ensure that the sleeve 56 is free to rotate with respect tothe primary shaft 44 when the primary shaft is being driven in thedirection which will cause the first spools 46 to wind in the straps 70so that the strap 76 will unwind freely from the spool 48 which willoffer very little resistance to unwinding and therefore will notsignificantly resist the opening of the door. When the door is to beclosed, the motor 40 will be driven in the opposite direction and theone-way clutch mechanisms 54 will ensure that the drive shaft 44 ispositively keyed to the sleeve 56. When, however, the rate at which thesecond straps 76 is wound in is greater than the payout speed of thestraps 70, the drag caused by the lower payout speed of the straps 70will cause the second spool 48 to slip with respect to the drive shaft44 so that the rate at which the strap 74 is wound in is equal to therate at which the strap 70 is paid out.

It will be noted that the diameter of the coiled strap 70 which islocated on the spools 46 will be at a minimum when the straps 70 arefully paid out and the door is in the closed position. It follows thatthe winding in torque will be at a maximum under these same conditions.This is extremely desirable because the maximum load conditions alsoexist when the door is at its lowermost position.

The power supply to the motor 40 is controlled so that it will be cutoff when the door reaches its fully open position or its fully closedposition. The power supply cut-off mechanism is illustrated in FIG. 3 ofthe drawings wherein it will be seen that limit switches 202 and 204 arelocated at opposite ends of a slot 110 which is formed in the base plate112 which is mounted on the header 36. The primary drive shaft 44 has athreaded portion 45 on which a nut 46 is threadedly mounted. An arm 47extends from the nut 46 into the slot 110. The arm 47 serves to preventrotation of the nut 46 while permitting longitudinal movement of the nut46 along the threaded portion 45 as the shaft 44 is rotatably driven.Rotation of the shaft 44 in one direction will caue the nut 46 to movetoward one or other of the limit switches 202 and 204 and will open thelimit switches 202 or 204 when the shaft 44 has rotated to a sufficientextent to fully open or fully close the door in use. The limit switches202 and 204 are mounted on support blocks 114 and 116 which are mountedon the shaft 118 so as to be positioned at any point along the lengththereof. The shaft 118 is supported by posts 119 which extend from thebase plate 112. Thus it will be seen that the extent to which the doorcan open or close can be adjusted by adjusting the position of the limitswitches 202 and 204.

Upper Door Panel Biasing Mechanism

As shown in FIG. 2 of the drawings, a biasing mechanism 90 is providedfor the purposes of "kicking" the upper edge portion of the upper ortrailing door panel 18a. The kicker 90 includes a mounting bracket 92which consists of a base plate 94 which is secured to the upper doorpanel 18a by means of mounting screws 96 and a hinge plate 98. The hingeplate 98 is secured in a face-to-face relationship to the base plate 94by means of the mounting screws 96 and is formed with a hinge channel100 and a lip portion 102. A second hinge plate 104 is formed with ahinge flange 106 at one end thereof and an eye 108 at the other endthereof. The hinge flange 106 is seated in the channel 100 so that thesecond hinge plate 104 is free to pivot relative to the door panel 18abetween a position in which it is arranged in a face-to-facerelationship with respect to the lip portion 102 and a position in whichit is arranged in a face-to-face relationship with respect to the doorpanel 18a. A spring 105 has one end clamped between the hinge plate 98and the base plate 94 and its other end bears against the second hingeplate 104. The spring 105 serves to urge the hinge plate 104 toward thedoor panel 18a. A stub shaft 110 of a roller 112 is mounted in the eye108. The roller 112 is mounted for movement in the guide track 14.

The second hinge plate 104 is proportioned to ensure that the upper ortrailing panel 18a can be located in an upright position even when theroller 112 is positioned on the curved portion 14b of the guide track14. It is not necessary to provide any biasing springs to urge the panel18a to the upright position because the panel 18a will be maintained inthe upright position by the forces applied to it by the second flexiblestrap member 76. The latch mechanism 250 will also serve to maintain thepanel 18a in the upright position.

Latch Mechanism

A latch mechanism is generally identified by the reference numeral 250in FIG. 7 of the drawings. The latch mechanism includes a pair of arms252 which are mounted on the shaft 44. As shown in FIG. 6 of thedrawings, one of the arms 252 is located between the annular flange 56and a collar 55. A friction fit is established between the arm 252 whichis located between the collar 55 and flange 56 by the pressure appliedthrough the spring 59. Similarly, the other arm 252 is retained betweenthe collar 60 and the collar 61. The compression spring 63 bears againstthe collar 61 and a further collar 65 which is secured to the shaft 44.The collar 61 is therefore pressed against the arm 252 by the spring 63.As a result, the arms 252 will tend to rotate about the axis of theshaft 44. The arms 252 are not, however, drivingly connected to theshaft 44 with the result that when the extent of movement of the arms252 is restricted, the arms will remain stationary while the shaft 44 isrotatably driven. A shaft 254 extends between the adjacent arms 252 andserves to connect the distal ends of the arms 252. A link arm 256extends downwardly from each arm 252. The link arms 256 are connected tothe distal ends of the lever arms 258. The proximal ends of the leverarms 258 are pivotally mounted on a shaft 260. A locking bar 262 extendstransversely between the distal ends of the lever arms 258. The shaft260 is mounted in the oppositely disposed side walls 264 of a supportbracket which is generally identified by the reference numeral 266. Thebracket 266 includes a base plate 268 which in use is mounted on thesill 35 (of the header 36) (FIG. 3).

A latch plate assembly 270 is mounted on the door panel 18a. The latchplate assembly 270 includes a mounting bracket 272 which is secured tothe door panel 18a by means of mounting bolts 274. The mounting bracket272 has a pair of lugs 276 which project from the upper end thereof. Ashaft 278 is mounted in and extends transversely between the lugs 276. Apair of arms 280 have their proximal ends pivotally mounted on the shaft278. A wedge-shaped locking bar 282 is mounted at and extendstransversely of the distal ends of the arms 280. The second flexiblestrap member 76 has one end looped around the shaft 278 and extendsbelow the locking bar 282. The second flexible strap 76 also extendsbelow the locking bar 262 and around the shaft 260.

In use, the winding in of the strap 76 causes the locking bar 282 topass under the locking bar 262 to assume the position shown in FIG. 8 ofthe drawings. When in this position, the drive motor can be deactivatedand the door will be retained in the locked position by the fact thatthe locking bar 282 cannot pass under the locking bar 262.

When the drive motor is activated for rotation in the direction requiredto open the door, the rotation of the shaft 44 in the direction of thearrow A will cause the arms 252 to rotate in the same direction. This inturn will raise the locking bar 262 above the locking bar 282 therebyreleasing the locking bar 282 to permit the second flexible strap 76 topay out.

It will be noted that as the strap 76 is being wound in, the shaft 44will be driven in a direction opposite to the direction indicated by theArrow A and consequently, the locking bar 262 will normally by urgeddownwardly toward the strap 76. The wedge-shaped configuration of thelocking bar 282 will, however, permit this bar to pass under the lockingbar 262 and the load which urges the bar 262 downwardly will cause thebar 262 to be lowered after the bar 282 passes inwardly therefrom toassume the position shown in FIG. 8.

Hinge Mechanism

The hinge mechanism used for connecting adjacent side edges of the doorpanels will now be described with reference to FIG. 2 of the drawings.As shown in FIG. 2 of the drawings, the hinge mechanism which isgenerally identified by the reference numeral 120 includes a first hingemember 122 and a second hinge member 124. Each hinge member 122,124 isformed from an extruded length of material such as a plastics materialand includes a body portion 126 which has first and second side walls128 and 130 and a bottom wall 132 which cooperate to form a generallyU-shaped channel 134. A plurality of hinge tubes 136 are located atspaced internals along the length of the first hinge member 122 and aplurality of similar hinge tubes 138 are located at spaced internalsalong the second hinge member 124. The first and second side walls 128and 130 have short flanges 140 and 142 extending inwardly from the outerends thereof. The side walls 128 are proportioned so as to be longerthan the side walls 130 so that the flanges 140 and 142 are not locateddirectly opposite one another. Channels 144 and channels 146 are formedin the marginal edge portion of the door panels 18. By offsetting thechannels 144 and 146, the cross-section of the partial edge portion isnot weakened to the extent that it would be if the channels 144 and 146were disposed directly opposite one another. A layer 133 of a flexibleplastics is extruded simultaneously with the bottom wall 132 such thatwhen the bottom walls 132 are arranged in a face-to-face relationshipwhen their associated wall panels are aligned in the closed position ofthe door, the flexible layers 133 will be compressed against one anotherto form a seal extending across the full width of the door.

A pivot pin 150 is extended longitudinally through the hinge tubes 136and 138 so as to pivotally connect the adjacent door penels. As shown inFIG. 1 of the drawings, when the door is in the closed position, thehinge tubes are not visible at the exterior surface of the door.

Rollers 112 are located on the ends of each of the pivot pins 150 andare arranged to run in the guide tracks 14.

In order to seal the lower edge of the door against the sill 32 when thedoor is in the closed position, a lower sealing member 152 is provided.The sealing member 152 is formed with substantially the same structureas the first hinge member 122 with the exception that two T-shaped slots154 are formed in the lower face of the bottom wall. A tubular extrusion156 is formed with T-shaped ribs 158 which extend longitudinally thereofand are proportioned to fit within the T-shaped slots 154. The tubularextrusion 156 has a chamber 160 located therein which permitscompression of the tubular extrusion 156. The tubular extrusion 156 ispreferably made from a flexible plastics material. A similar tubularextrusion 156 is provided on the header 36 (FIG. 3) to provide a sealbetween the door panel 18a and the sill rail 35 of the header 36. AnL-shaped extrusion 163 is mounted on the sill rail 35. The upright arm167 of the L-shaped extrusion is formed with a pair of T-shaped slots(not shown) to receive the T-shaped mounting ribs of the tubularextrusion 156.

As shown in FIG. 4 of the drawings, each of the jam members 34 is formedwith a U-shaped channel 162 which extends longitudinally thereof. Aflexible sealing web 164 has one edge secured within the channel 162 bymeans of a mounting clip 166 which is secured by mounting screws 168 tothe side wall 170 of the jam member 34. The flexible sealing web 164 hasa sufficient length to extend into contact with the outer surface of themarginal edge portions of the adjacent door panels. The sealing webs 164extend over the full height of the jam members 34 and serves to seal theside edges of the door along the full length of the door when it is inthe closed position.

Method of Opening and Closing Door

When the door is in the closed position, it can be opened by activatinga control system which is described hereinafter which serves to powerthe drive motor 40 so that it will rotate in a first direction whichwill cause rotation of the primary drive shaft 44 in the directionrequired to wind in the first flexible strap members 70. This will causethe door to move toward the open position. Because the straps 70 areconnected to the lower door panel 18b, the only load which is applied tothe door panels which are located above the lower panel 18b are loadswhich push the preceding panels along the guide tracks. These pushingforces permit the preceding door panels 18 to articulate freely alongthe track and this facilitates the manipulation around the curvedportion of the track.

As previously indicated, the second spool 48 can slip to permit thepayout rate of the second flexible member 76 to match the wind-in rateof the first flexible member 70.

When the door is fully opened, the trailing or lower door panel 18b willobscure the winching mechanism 16 and protect it from damage duringloading and unloading of the container compartment.

In order to close the door, the control system is operated to drive themotor 40 in the opposite direction thereby causing the second spool 48to wind in the strap 76 so that the door is pulled to the closedposition by a load applied to the upper door panel 18a. The rotation ofthe motor 40 in the opposite direction drives the first spools 46 in thedirection required to payout the straps 70. Again by effectively pushingthe door to the closed position by applying a load to the trailing doorpanel, the door panels will articulate freely when being driven aroundthe curved portion of the track and therefore negotiate the curvedportion of the track without difficulty. As previously indicated, thevariation in wind-in and payout speeds of the straps 76 and 70 isaccommodated by the slipping clutch mechanism.

From the foregoing it will be apparent that the door of the presentinvention can be powered from the open position to the closed positionand from the closed position to the open position as required in use.

Electrical Controls

A control system suitable for use in controlling the opening and closingof the doors illustrated in FIG. 9 of the drawings and is generallyidentified by the reference numeral 180. The control system is designedto control the direction of rotation of the reversible D.C. motor 40.

The control system 180 includes a first motor driving circuit 182 and asecond motor driving circuit 184 which serve to supply power to themotor 40 from a D.C. source through a line 186 and branch lines 186a and186b. A first pair of switches 188 and a second pair of switches 190 arelocated in the first motor driving circuit 182 and in the second motordriving circuit 184 respectively.

A first control circuit which is generally identified by the referencenumeral 196 is provided for controlling the movement of the first pairof switches 188 of the first motor driving circuit 182 and a secondcontrol circuit is provided for the purposes of controlling the movementof the second pair of switches 190 which are located in the second motordriving circuit 184. The first control circuit 196 comprises a primaryrelay 192a and a secondary relay 192b which are connected in parallel.The primary relay 192a is operable to control the movement of the firstpair of switches 188. A first control switch 222 acts as a self-latchingswitch which is associated with the secondary relay 192b. A first powersupply line 200 is connected through a branch 200a to the first controlcircuit 196 and through a branch 200b to the second control circuit 198.A first normally closed limit switch 202 is provided in the branch line200a and a second normally closed limit switch 204 is provided in thebranch line 200b.

The second control circuit 198 includes a second control switch 224which is associated with the secondary relay 194.

The first control switch 222 and second control switch 224 serve as themaster control switches which are manually operable to cause rotation ofthe motor 40 in one direction or the other to raise or lower the door isrequired in use. The first control switch 222 has a first terminal 230,a second terminal 234 and a base terminal 226. The second control switch224 has a first terminal 232, a second terminal 236 and a base terminal228. The base terminals 226 and 228 are connected to one another by agrounding line 220. The first terminals 230 and 232 of the first switch222 and second switch 224 are connected to one another by the groundingline 216.

A slave control system is provided which is generally identified by thereference numeral 380. The slave control system 380 includes a firstslave control switch 322 and a second slave control switch 324. Thefirst slave control switch 322 has a first terminal 330, a secondterminal 334 and a base terminal 326. The second slave control switch324 has a first terminal 332, a second terminal 336 and a base terminal328. A first slave relay 392 is connected in parallel with the relays192a and 192b through lines 331 and 333. A second slave relay 394 isconnected in parallel with the relays 194a and 194b through lines 335and 337. An on/off push-button switch generally identified by thereference numeral 339 has switch members 341 in each of the lines 331,333, 335 and 337. The on/off push-button switch 339 is operable toactivate or deactivate the slave control system as required in use. Aline 343 connects the grounding line 216 of the master control system tothe line 331 of the slave control. An LED 345 is provided in the line343 to provide a visual indication that the slave control circuit isarmed when the push button switch 339 is in the position required to armthe slave control circuit. A grounding line 347 is connected to theterminals 330 and 332 of the slave control switches 322 and 324.

A control switch 185 is provided in the power supply line 186 forinterrupting the supply of power from the 12-volt power supply system ofthe vehicle. A relay 187 is associated with the switch 185. The relay187 is connected through a line 189 to the ignition control switch whichis generally the key-operated ignition switch of the vehicle so thatpower can only be supplied to the system when the ignition switch isoperated.

In use, the when the door is in its fully closed position, the limitswitch 202 will be closed and the limit switch 204 will be open. Whenthe system is activated through the ignition control switch, power issupplied from the 12-volt power supply through the switch 185 and line186 to arm the first and second motor driving circuits. Power is alsosupplied through the line 200, switch 202 and line 200a to arm the firstcontrol circuit 196. When the door is to be raised, the first controlswitch 22 is manually activated to move its switch member from theposition shown in solid lines in FIG. 1 to the position contacting thesecond terminal 234. When in this position, the secondary relay 192 isoperable to latch the switch member of the switch 222 in its operableposition grounding the first control circuit. The first control circuit196 is grounded through the switch 222, switch 224, lines 216, 343 andslave switches 322 and 324 to ground line 347. When the first controlcircuit 196 is activated, the primary relay 192 is operable to cause thefirst motor switches 188 to move from the open position shown in solidlines in FIG. 9 to a closed position completing the first motor drivingcircuit 182. The motor 40 will continue to rotate in the directionrequired to open the door until either the second master control switch224 is manually operated to break the connection between the baseterminal 228 and the first terminal 232 to interrupt the groundingcircuit or until the limit switch 202 is opened by reason of the doorreaching the upper limit of its travel as previously described.

The second control circuit 198 operates to raise the door in response tomanual operation of the switch 224 in the same manner as that previouslydescribed and will not therefore be described in detail.

When the on/off push-button 393 is operated to arm the slave controlcircuit 380, it is possible to drive the motor 40 in the first directionby operating either the master control switch 222 or the slave controlswitch 322 and it is possible to drive the motor 40 in the oppositedirection by operating the master control switch 224 or the slavecontrol switch 324. In order to activate the motor 40 to open the doorby using the slave control system, the slave control switch 322 ismanually displaced from the position shown in solid lines in FIG. 9 tomake contact with the terminal 334. This permits the first controlcircuit 196 to be grounded through the line 333, terminal 334, terminal326, terminal 328, terminal 332 and ground line 347. Simultaneously, therelay 392 is activated to latch the switch 322 in its operable positionin contact with the terminal 334. Again, the motor 40 will be driven inthe required direction until either the limit switch 202 is opened orthe slave control switch 324 is operated. The slave control switch 324is similarly operable to cause the motor 40 to be driven in thedirection required to close the door and its operation can beinterrupted by operating the slave control switch or the opening of thelimit switch 204.

It will be apparent that when the slave control switch 339 is in theposition required to activate the control switch, it is possible toinitiate rotation of the motor 40 in one direction by operating one ofthe control switches of the master control and to interrupt the movementof the motor and/or cause rotation in the opposite direction byactivating the appropriate slave control switch.

It will also be apparent that when both master control switches 222 and224 are manually depressed simultaneously or both slave control switches322 and 324 are depressed simultaneously, the power supply to the motor40 can be interrupted at any time during the raising or lowering of thedoor. This gives the operator the opportunity to stop the movement ofthe door or reverse the direction of movement of the door at any time ifthis is required for safety purposes.

In use, the master control switches may be located in the drivercompartment and the slave control switches may be located at a pointadjacent the door. Consequently, if the vehicle is to be used fordelivering small loads such as parcels, it is possible for the driver toactivate the master control switch to cause the door to begin to openbefore he leaves the driver compartment. As a result, when he arrives atthe rear end of the vehicle, the door will be at least partially open.He can then remove the parcel which is to be delivered and immediatelythereafter activate the slave control switch to cause the door to movetowards its closed position.

Various modifications of the present invention will be apparent to thoseskilled in the art. One such modification is illustrated in FIGS. 10, 11and 12 wherein the reference numeral 400 refers generally to a latchsocket housing and the reference numeral 402 refers generally to a latchplug. The latch socket housing 400 comprises a U-shaped housing 404which has a top wall 406, a bottom wall 408 and a back wall 410. A notch412 is formed in the top wall 406 centrally of the width thereof. Thetop, bottom and back walls cooperate with one another to form a U-shapedsocket 414 therebetween. The top wall 412 has a flange portion 416 whichextends upwardly and forwardly therefrom which serves to guide the latchplug 403 into the notch 414 in use. A pair of end plates 418 are mountedin the socket 414 at opposite sides thereof and are secured to the top,bottom and side walls. A guide roller 420 is mounted for rotation in theend plates 418. The guide roller 420 serves to guide the flexible strapmember 76 into the socket 414 through the open end thereof and out ofthe socket through the notch 412. A pair of pins 422 have their oppositeends mounted in elongated slots 424 formed in the top and bottom walls406 and 408 respectively. The slots 424 which are formed in each wallare arranged to converge with one another in a direction toward theentranceway to the socket 414. Tension springs 426 are connected to andextend between the pins 422 and are pretensioned to apply a load to thepins 422 which urges them to their forward position shown in FIG. 10. Amounting bracket 428 is secured to the bottom wall 408 and serves tomount the socket housing 400 in the position assumed by the supportbracket 266 of the latch mechanism illustrated in FIG. 3 which, aspreviously indicated, is located in the header cavity 38.

The latch plug 402 comprises a pair of lugs 430 which are mounted on theupper edge of a door panel 18a. A bar 432 has its opposite endspivotally mounted in the lugs 430. A pair of face plates 434 and 436have their proximal ends mounted on the bar 432 and extend forwardlytherefrom in a spaced parallel relationship to provide a compartment 438therebetween. A pair of spacer pins 440 are located at the distal endsof the face plates 434 and 436 and extend therebetween. The spacer pins440 serve to space the distal ends of the face plates 434 and 436 withrespect to one another. A pair of latch levers 442 are pivotally mountedin the compartment 438 by means of pivot pins 444. The latch levers 442each have an outer end portion 446 which projects from the pivot pin 444toward the distal end of the plug and an inner end 448 which projectstoward the proximal end of the plug. The outer end of each lever arm ishook-shaped and has a recess 450 which is shaped in proportioned tointerlock with the locking pins 442 when the plug is seated in thesocket. A shoulder 452 is formed on the inner face of each lever. Alocking bar 454 is slidably mounted in the compartment 438 and extendstransversely between the inner side faces of the latch levers 442. Thelocking bar has a sufficient length to bear against the inner side facesof the latch levers to cause the levers to be pivotted outwardly to theextended position shown in FIG. 11 when the locking bar is located inits forward position. The inner end portions 448 of each lever arearranged to bear against the bar 432 when the latch levers are in theextended position so as to limit the extent to which the outer endportions 446 may project from the side edges of the face plates 434 and436. It will be noted that the side edges of the plates 434 and 436converge in a direction toward the distal end thereof so as to begenerally wedge-shaped to facilitate the passage of the distal endthereof inwardly between the latch pins 422 as will be describedhereinafter. The locking pin 454 is movable between the locking positionshown in FIG. 11 in solid lines and a release position in which it islocated more closely adjacent the proximal end of the face plates 434and 436. A tension spring 458 has its opposite ends secured to the outerend portions of the latch levers 442. The tension spring 458 ispreloaded so that it will normally serve to urge the latch lever armstoward a retracted position with respect to the compartment 438.

Passageways 456 are formed in the face plates 434 and 436 through whichan end of the belt 76 is looped so that the belt 76 will bear againstthe locking pin 454. It will be noted that when the belt 76 is pulled inthe direction of the arrow B, it will bear against the locking pin 454causing it to move toward the distal end of the plug and this in turnwill cause the latch levers to be pivotted to the extended positionshown in FIG. 11 in which the recesses 450 are located outwardly fromthe side edges of the face plate 434, 436. When the pulling force isremoved from the belt 76, the tension spring 458 will serve to draw theouter end portions 446 of the latch levers 442 inwardly toward oneanother to a retracted position. This will have the effect of causingthe locking pin 454 to be deflected toward the proximal end of the latchplug.

As previously described, when the door is to be closed, the belt 76 iswound in. This will eventually cause the latch plug to be drawn inwardlywith respect to the latch socket housing. It will also apply a tensileload to the belt 76 in the direction of the arrow B and as previouslydescribed, this will have the effect of locating the latch lever arms intheir extended position illustrated in FIG. 11. As the distal end of theplug begins to enter the socket 414, the outer end portions of the leverarms will bear against the latch pins 422. Because the distance betweenthe outer end portions of the lever arms when in the extended position,is greater than the distance between the latch pins 422 when they are intheir innermost position illustrated in FIG. 10, the arms 446 willengage the latch pins 442 and cause them to be deflected rearwardly andoutwardly away from one another until they are spaced a sufficientdistance to permit the outer end portions of the latch levers to passtherebetween. As soon as the outer end portions of the lever arms arelocated inwardly of the latch pins 422, the tension spring 426 willserve to draw the pins 442 to their original position. This will locatethe pins 422 in the recesses 450. As a result, as long as tension ismaintained in the belt 76, the lever arms 446 will be maintained in aninterlocking relationship with the locking pins 422 which will serve toprevent opening of the door.

When the tension in the belt 76 is relieved as for example, when adirection of rotation of the drive motor 40 is reversed, the tensionspring 456 will serve to draw the outer end portions of the latch leverarms inwardly to their retracted position so as to release the latchpins 422 from the recesses 450 so that when the door opening forces areapplied, the latch plug can be freely withdrawn from the latch socket.

From the foregoing, it will be apparent that this latch mechanismprovides a simple and effective self-locking latch for a powered doorassembly.

We claim:
 1. A drive mechanism for raising and lowering a roll-up doorcomprising;(a) a primary drive shaft, (b) first and second windingspools mounted on said primary drive shaft, each winding spool having awinding drum, (c) first and second winding straps each having first andsecond ends, the first end of the first strap being mounted on thewinding drum of the first spool and the second end of the first strapbeing connected to one end of a roll-up door, the first end of thesecond strap being mounted on the winding drum of the second spool andthe second end of the second strap being connected to the other end ofthe roll-up door, the winding drums and straps being proportioned tocause each successive turn of each strap to be wound upon one another asthe straps are wound in such that the effective diameter of the windingsurface of each winding drum will vary as its associated strap is woundin or paid out, (d) slipping clutch means communicating between saidprimary shaft and one of said winding spools to permit said one of saidwinding spools to slip with respect to said primary drive shaft toaccommodate the difference between the effective diameter of the windingsurface of the winding drums such that the first and second windingdrums may both be driven by the primary drive shaft.
 2. A drivemechanism as claimed in claim 1 wherein two first winding spools aremounted on said primary drive shaft adjacent opposite ends thereof andare fixed to the primary drive shaft for rotation therewith, said secondspool being located between said first winding spools and beingdrivingly connected to said primary shaft by said slipping clutch.
 3. Adrive mechanism as claimed in claim 2 wherein said second end of saidsecond winding strap is connected to the upper end of said door and thesecond ends of said first straps are connected to the lower end of saiddoor such that the effective diameter of the winding surface of thefirst winding drums increases progressively as the first straps arewound in to provide maximum torque during the initial stage of the liftwhen the effective weight of the door is at its greatest.